LIFE IN SECONDARY TIMES 253 



which multiplied so rapidly during the Jurassic Period, were 

 limited during that period to the Leptolepididae, but afterwards 

 became very varied. The majority at first, as we should expect, 

 had pectoral and pelvic fins far apart like those of the Sharks 

 and Ganoids, and fifteen families can be enumerated, many of 

 them specialized. Among them were families which still 

 thrive, such as the Scopelidae, now pelagic and resembling the 

 Salmon ; Clupeidae, closely related to our Sardines and 

 Herrings ; 1 the deep-water Halosauridse ; Osteoglossidae, and 

 even Murenidse, which have lost their fins. 2 Fishes with pelvic 

 fins close to the pectoral also made their appearance in the 

 form of the Berycidae, representatives of which still exist. 



It is thus an already quite important fauna, consisting of 

 agile Fishes, whose very moderate size enabled them to find 

 their way everywhere ; hence they must have made life 

 very difficult for the Ammonites ; not only pursuing them, 

 but competing with them for food. This must be taken into 

 consideration if an explanation of the disappearance of the 

 great swimming molluscs is sought. Those that lived under 

 special conditions — for instance, the Cretaceous C-shaped 

 Ammonites, which lived suspended in mid-water far from the 

 surface, persisted much longer than the others, because the 

 zone they inhabited was relatively poor in large-sized prey and 

 little frequented by Fishes. 



Let us now turn our eyes to the land. The sombre and 

 monotonous vegetation of the Primary Period still persisted, 

 for the most part, during the Triassic and Jurassic, but in the 

 Cretaceous the virgin countryside was brightened by many a 

 different shade of young foliage and brilliant flowers. The 

 trees we know to-day uplifted their capriciously branched 

 trunks somewhat shyly at first among the severely regular 

 stems and arms of the primitive conifers ; but they ended by 

 driving them out of the plains, and Poplars, Willows, Birches, 

 Beaches, Oaks, Walnuts, Plane-trees, and Maples, the first 

 branches of the theoretical genealogical tree we set up a few 

 pages earlier, crowded into their place. The surface of the earth 

 became covered with vast forests in which there grew also 

 F"igs, Bread-fruit trees, and other unisexual flowering Urticeae. 

 Holly, Ivy, and different members of the Cornaceas family 

 sprang up in their shelter, and even some gamopetalous 



1 Diplomistus, Scombroclupea. 2 Urenchelys. 



